Lying Around Doesn't Matter If You Exercise

It's an age-old cry from parents: "Stop lying around in front of that TV/computer/console and get some exercise!" However, a new study suggests that the biggest impact on child health comes from the amount of time spent being active, not the amount of sedentary behaviour.

The study, published in the Journal of the American Medical Association (JAMA), assessed the risk factors for indicators of potential cardiometabolic risks (including waist size, blood pressure and cholesterol levels) in 20,000 children and adolescents, using data from 14 previous studies. Some previous research has suggested that the benefits of exercise (moderate- to vigorous-intensity physical activity or MVPA, as the study terms it) can be offset by large periods of inactivity. However, the study failed to find any correlation between the two:

The researchers found that time in MVPA was significantly associated with all cardiometabolic outcomes independent of sex, age, accelerometer monitor wear time, time spent sedentary, and waist circumference (when not the outcome). Time spent sedentary was not associated with any of the outcomes after additional adjustment for MVPA.

To be clear, no-one is disputing that kids (and everybody) need at least an hour a day of vigorous exercise to stay healthy. The health benefits for more active kids were obvious in the study. But if they're achieving that, you don't need to worry so much about time spent on less active pursuits.